Noradrenergic Control of Arginine Vasopressin Release from the Ewe Hypothalamus In Vitro: Sensitivity to Oestradiol

The present study aims at ascertaining the influence of α₁‐adrenoreceptors on arginine vasopressin (AVP) release in vitro and determine whether E₂ modulates the α₁‐adrenoreceptor and AVP interaction. Ten minutes after ewe killing, sagittal midline hypothalamic slices (from the anterior preoptic area to the mediobasal hypothalamus with the median eminence, 2 mm thick, 2 per sheep) were dissected, placed in oxygenated minimum essential media‐α (MEM‐α) at 4°C and within 2 h were singly perifused at 37°C with oxygenated MEM‐α (pH 7.4; flow rate 0.15 ml/min), either with or without E₂ (24 pg/ml). After 4 h equilibration, 10 min fractions were collected for 4 h interposed with 10 min exposure at 60 min to a specific α₁‐adrenoreceptor agonist or antagonist at various doses (0.1–10 mm ). At the end of all perifusions, slices responded to KCl (100 mm ) with AVP efflux (p < 0.05). Release of AVP was enhanced (p < 0.05) by the α₁‐adrenoreceptor agonist (methoxamine 10 mm ; no E₂, n = 7 perifusion chambers: from 14.3 ± 2.7 to 20.9 ± 3.9, with E₂, n = 10: from 10.7 ± 1.2 to 18.4 ± 3.4 pg/ml) or the antagonist (thymoxamine 10 mm ; no E₂, n = 5: from 9.5 ± 3.1 to 30.4 ± 6.0, with E₂, n = 10: from 10.8 ± 0.9 to 39.1 ± 6.3 pg/ml). With the agonist, the response occurred only at 80 min (p < 0.05) both in the presence and absence of E₂. Whereas, after the antagonist, values were higher (p < 0.05) throughout the post‐treatment period (80–170 min) without E₂, but declined by 150 min in the presence of E₂. Furthermore, the response to the α₁‐adrenoreceptor antagonist was greater (p < 0.05; 90–140 min) than the agonist only in the presence of E₂. In conclusion, these results reveal direct α₁‐adrenoreceptor‐mediated control of the hypothalamic AVP neuronal system which is modulated by E₂.     

Leucoencephalomyelopathy in Australian Rottweiler dogs

Clinical and pathological studies of a neurological disorder of 3 adult Rottweiler dogs are described. Dogs developed proprioceptive losses involving the limbs, leading to progressively worsening ataxia and hypermetria. Blood and CSF fluid analyses were normal and radiographs and myelograms showed no compressive lesions of the spinal cord. At necropsy, severe demyelination of the dorsal and lateral funiculi of the cervical spinal cord was visible grossly. Microscopically there was more extensive, symmetrical involvement of the spinal cord and brain than was apparent grossly, with demyelination of white matter tracts and sparing of axons in affected areas. These changes were considered diagnostic for leucoencephalomyelopathy. This condition has not been previously reported in Australia, and is probably transmitted genetically, presumably as an autosomal recessive trait.     

Acoustic tracking of ocean-dumped sewage sludge

With a modified 200-kilohertz acoustic echo sounder, it has been possible to detect and map sewage dumped into the ocean over several hours. The three-dimensional distribution of suspended material and its rate of diffusion are indicated after digital processing of the data.     

Identification of the 1H-NMR spectra of complex oligosaccharides with artificial neural networks

Artificial networks can be used to identify hydrogen nuclear magnetic resonance (1H-NMR) spectra of complex oligosaccharides. Feed-forward neural networks with back-propagation of errors can distinguish between spectra of oligosaccharides that differ by only one glycosyl residue in twenty. The artificial neural networks use features of the strongly overlapping region of the spectra (hump region) as well as features of the resolved regions of the spectra (structural reporter groups) to recognize spectra and efficiently recognized 1H-NMR spectra even when the spectra were perturbed by minor variations in their chemical shifts. Identification of spectra by neural network-based pattern recognition techniques required less than 0.1 second. It is anticipated that artificial neural networks can be used to identify the structures of any complex carbohydrate that has been previously characterized and for which a 1H-NMR spectrum is available.     

The gene or not the gene--that is the question: understanding the genetically engineered mouse phenotype

Embryonic stem cells have had a significant impact on understanding gene function and gene interactions through the use of genetically engineered mice. However, the genetic context (ie, mouse strain) in which these modifications in alleles are made may have a considerable effect on the phenotypic changes identified in these mice. In addition, tissue- and time-specific gene expression systems may generate unanticipated outcomes. This article discusses the history of embryonic stem cells, reviews how mouse strain can affect phenotype (using specific examples), and examines some of the caveats of conditional gene expression systems.     

Clinical,Ultrasonographic and Pathological Findings in a Bull with Segmental Aplasia of the Mesonephric Duct

On assessment for use in an AI stud, a 12‐month‐old bull was found to produce low volume ejaculates with 41% of the sperm having morphological abnormalities. No left epididymal tail was palpable and the head of the epididymis on the left was twice the size compared with the right. Ultrasound examination showed the left testis to contain a large central area of decreased echogenicity, which could be followed proximally to a 15‐mm echolucent lesion at the site of the epididymal head. Postmortem examination revealed a 15‐mm diameter cyst in the region of the left epididymal head, and absence of the body and tail of the epididymis. The mediastinum testis of the left testis was dilated, corresponding to the area of decreased echogenicity observed on ultrasonography. No left seminal vesicle was present and the ampulla was significantly smaller than the same structure on the right. Histological examination revealed incomplete or absent spermatogenesis involving the majority of seminiferous tubules in the left testis, and a small proportion of those of the right testis. The cystic structure at the site of the left epididymal head was lined by irregular, sometimes attenuated, epithelium and contained sparse spermatozoa. This case demonstrates the adverse impact, which segmental aplasia of the mesonephric duct had on the testicular and epididymal function of a bull, and highlights the importance of careful clinical assessment in its diagnosis.